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Exercise #11: Hours, Minutes, Seconds

getHoursMinutesSeconds(90) → '1m 30s'

Websites often use relative timestamps such as “3 days ago” or “about 3h ago” so the user doesn’t need to compare an absolute timestamp to the current time. In this exercise, you write a function that converts a number of seconds into a string with the number of hours, minutes, and seconds.

Exercise Description

Write a getHoursMinutesSeconds() function that has a totalSeconds parameter. The argument for this parameter will be the number of seconds to be translated into the number of hours, minutes, and seconds. If the amount for the hours, minutes, or seconds is zero, don’t show it: the function should return '10m' rather than '0h 10m 0s'. The only exception is that getHoursMinutesSeconds(0) should return '0s'.

These Python assert statements stop the program if their condition is False. Copy them to the bottom of your solution program. Your solution is correct if the following assert statements’ conditions are all True:

assert getHoursMinutesSeconds(30) == '30s'

assert getHoursMinutesSeconds(60) == '1m'

assert getHoursMinutesSeconds(90) == '1m 30s'

assert getHoursMinutesSeconds(3600) == '1h'

assert getHoursMinutesSeconds(3601) == '1h 1s'

assert getHoursMinutesSeconds(3661) == '1h 1m 1s'

assert getHoursMinutesSeconds(90042) == '25h 42s'

assert getHoursMinutesSeconds(0) == '0s'

For an additional challenge, break up 24 hour periods into days with a “d” suffix. For example, getHoursMinutesSeconds(90042) would return '1d 1h 42s'.

Try to write a solution based on the information in this description. If you still have trouble solving this exercise, read the Solution Design and Special Cases and Gotchas sections for additional hints.

Prerequisite concepts: join(), append(), lists, string concatenation, while loops

Solution Design

One hour is 3600 seconds, one minute is 60 seconds, and one second is… 1 second. Our solution can have variables that track the number of hours, minutes, and seconds in the final result with variables hours, minutes, and seconds. The code subtracts 3600 from the totalSeconds while increasing hours by 1. Then the code subtracts 60 from totalSeconds while increasing minutes by 1. The seconds variable can then be set to whatever remains in totalSeconds.

After calculating hours, minutes, and seconds, you should convert those integer amounts into strings with respective 'h', 'm', and 's' suffixes like '1h' or '30s'. Then you can append them to a list that initially starts as empty. Then the join() list method can join these strings together with a single space separating them: from the list ['1h', '30s'] to the string '1h 30s'. For example, enter the following into the interactive shell:

>>> hms = ['1h', '30s']

>>> ' '.join(hms)

'1h 30s'

The function then returns this space-separated string.

If you’re unfamiliar with the join() string method, you can enter help(str.join) into the interactive shell to view its documentation, or do an internet search for “python join”.

Special Cases and Gotchas

The first special case your function should check for is if the totalSeconds parameter is set to 0. In this case, the function can immediately return '0s'.

The final result string shouldn’t include hours, minutes, or seconds if the amount of those is zero. For example, your program should return '1h 12s' but not '1h 0m 12s'.

Also, it’s important to subtract the larger amounts first. Otherwise, you would, for example, increase hours by 0 and minutes by 120 instead of increase hours by 2 and minutes by 0.

Now try to write a solution based on the information in the previous sections. If you still have trouble solving this exercise, read the Solution Template section for additional hints.

Solution Template

Try to first write a solution from scratch. But if you have difficulty, you can use the following partial program as a starting place. Copy the following code from https://invpy.com/hoursminutesseconds-template.py and paste it into your code editor. Replace the underscores with code to make a working program:

def getHoursMinutesSeconds(totalSeconds):

# If totalSeconds is 0, just return '0s':

if totalSeconds == ____:

return ____

# Set hours to 0, then add an hour for every 3600 seconds removed from

# totalSeconds until totalSeconds is less than 3600:

hours = 0

while totalSeconds ____ 3600:

hours += ____

totalSeconds -= ____

# Set minutes to 0, then add a minute for every 60 seconds removed from

# totalSeconds until totalSeconds is less than 60:

minutes = 0

while totalSeconds >= ____:

minutes += 1

totalSeconds -= ____

# Set seconds to the remaining totalSeconds value:

seconds = ____

# Create an hms list that contains the string hour/minute/second amounts:

hms = []

# If there are one or more hours, add the amount with an 'h' suffix:

if hours > ____:

____.append(str(____) + 'h')

# If there are one or more minutes, add the amount with an 'm' suffix:

if minutes > 0:

hms.append(____(minutes) + 'm')

# If there are one or more seconds, add the amount with an 's' suffix:

if seconds > 0:

hms.append(str(seconds) + ____)

# Join the hour/minute/second strings with a space in between them:

return ' '.join(____)

The complete solution for this exercise is given in Appendix A and https://invpy.com/hoursminutesseconds.py. You can view each step of this program as it runs under a debugger at https://invpy.com/hoursminutesseconds-debug/.

Alternate Solution Design

Alternatively, instead of subtractions in a loop you can use Python’s // integer division operator to see how many 3600 amounts (for hours) or 60 amounts (for minutes) fit into totalSeconds. To get the remaining amount in totalSeconds after removing the seconds accounted for hours and minutes, you can use Python’s % modulo operator.

For example, if totalSeconds were 10000, then 10000 // 3600 evaluates to 2, telling you that there are two hours in 10,000 seconds. Then 10000 % 3600 evaluates to 2800, telling you there are 2,800 seconds left over after removing the two hours from 10,000 seconds. You would then run 2800 // 60 to find the number of minutes in 2,800 seconds and 2800 % 60 to find the number of seconds remaining after removing those minutes.

Alternate Solution Template

Try to first write a solution from scratch. But if you have difficulty, you can use the following partial program as a starting place. Copy the following code from https://invpy.com/hoursminutesseconds2-template.py and paste it into your code editor. Replace the underscores with code to make a working program:

def getHoursMinutesSeconds(totalSeconds):

# If totalSeconds is 0, just return '0s':

if totalSeconds == ____:

return ____

# Set hours to how many times 3600 seconds can divide

# totalSeconds. Then set totalSeconds to the remainder:

if totalSeconds >= 3600:

hours = totalSeconds // 3600

totalSeconds = totalSeconds % 3600

else: